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Purpose In the context of oropharyngeal cancer treated with definitive radiotherapy, the aim of this retrospective study was to identify the best threshold value to compute metabolic tumor volume (MTV) and/or total lesion glycolysis to predict local-regional control (LRC) and disease-free survival.

Methods One hundred twenty patients with a locally advanced oropharyngeal cancer from 2 different institutions treated with definitive radiotherapy underwent FDG PET/CT before treatment. Various MTVs and total lesion glycolysis were defined based on 2 segmentation methods: (i) an absolute threshold of SUV (0–20 g/mL) or (ii) a relative threshold for SUVmax (0%–100%). The parameters’ predictive capabilities for disease-free survival and LRC were assessed using the Harrell C-index and Cox regression model.

Conclusions The use of different thresholds within a reasonable range (between 5.5 and 7 for an absolute threshold and between 40% and 68% for a relative threshold) seems to have no major impact on the predictive value of MTV. This parameter may be used to identify patient with a high risk of recurrence and who may benefit from treatment intensification.

Received for publication October 20, 2016; revision accepted January 15, 2017.

Conflicts of interest and sources of funding: This work was partly supported by the Swiss National Science Foundation with grant agreement PZ00P2_154891 (to A. Depeursinge). None declared to all other authors.